[rubygems/rubygems] Added missing require for Bundler::YAMLSerializer
https://github.com/rubygems/rubygems/commit/55ef32fdd7
[rubygems/rubygems] Added missing require for Bundler::YAMLSerializer
https://github.com/rubygems/rubygems/commit/55ef32fdd7